diff --git a/src/client/client_node_rpcs.ml b/src/client/client_node_rpcs.ml
index b2eb0ddc9..e2d3db550 100644
--- a/src/client/client_node_rpcs.ml
+++ b/src/client/client_node_rpcs.ml
@@ -18,9 +18,11 @@ let errors cctxt =
 let forge_block_header cctxt header =
   call_service0 cctxt Services.forge_block_header header
 
-let inject_block cctxt ?(async = false) ?(force = false) raw operations =
+let inject_block cctxt
+    ?(async = false) ?(force = false) ?net_id
+    raw operations =
   call_err_service0 cctxt Services.inject_block
-    { raw ; blocking = not async ; force ; operations }
+    { raw ; blocking = not async ; force ; net_id ; operations }
 
 let inject_operation cctxt ?(async = false) ?force ?net_id operation =
   call_err_service0 cctxt Services.inject_operation
diff --git a/src/client/client_node_rpcs.mli b/src/client/client_node_rpcs.mli
index e5697680f..ef64e93c4 100644
--- a/src/client/client_node_rpcs.mli
+++ b/src/client/client_node_rpcs.mli
@@ -19,7 +19,7 @@ val forge_block_header:
 
 val inject_block:
   config ->
-  ?async:bool -> ?force:bool ->
+  ?async:bool -> ?force:bool -> ?net_id:Net_id.t ->
   MBytes.t -> Operation.t list list ->
   Block_hash.t tzresult Lwt.t
 (** [inject_block cctxt ?async ?force raw_block] tries to inject
diff --git a/src/client/embedded/alpha/client_baking_blocks.ml b/src/client/embedded/alpha/client_baking_blocks.ml
index 29096c460..c63708d4c 100644
--- a/src/client/embedded/alpha/client_baking_blocks.ml
+++ b/src/client/embedded/alpha/client_baking_blocks.ml
@@ -9,6 +9,7 @@
 
 type block_info = {
   hash: Block_hash.t ;
+  net_id: Net_id.t ;
   predecessor: Block_hash.t ;
   fitness: MBytes.t list ;
   timestamp: Time.t ;
@@ -17,21 +18,22 @@ type block_info = {
 }
 
 let convert_block_info cctxt
-    ( { hash ; predecessor ; fitness ; timestamp ; protocol }
+    ( { hash ; net_id ; predecessor ; fitness ; timestamp ; protocol }
       : Client_node_rpcs.Blocks.block_info ) =
   Client_proto_rpcs.Context.level cctxt (`Hash hash) >>= function
   | Ok level ->
       Lwt.return
-        (Some { hash ; predecessor ; fitness ; timestamp ; protocol ; level })
+        (Some { hash ; net_id ; predecessor ;
+                fitness ; timestamp ; protocol ; level })
   | Error _ ->
       (* TODO log error *)
       Lwt.return_none
 
 let convert_block_info_err cctxt
-    ( { hash ; predecessor ; fitness ; timestamp ; protocol }
+    ( { hash ; net_id ; predecessor ; fitness ; timestamp ; protocol }
       : Client_node_rpcs.Blocks.block_info ) =
   Client_proto_rpcs.Context.level cctxt (`Hash hash) >>=? fun level ->
-  return { hash ; predecessor ; fitness ; timestamp ; protocol ; level }
+  return { hash ; net_id ; predecessor ; fitness ; timestamp ; protocol ; level }
 
 let info cctxt ?include_ops block =
   Client_node_rpcs.Blocks.info cctxt ?include_ops block >>=? fun block ->
diff --git a/src/client/embedded/alpha/client_baking_blocks.mli b/src/client/embedded/alpha/client_baking_blocks.mli
index fac1225c1..661c9e81c 100644
--- a/src/client/embedded/alpha/client_baking_blocks.mli
+++ b/src/client/embedded/alpha/client_baking_blocks.mli
@@ -9,6 +9,7 @@
 
 type block_info = {
   hash: Block_hash.t ;
+  net_id: Net_id.t ;
   predecessor: Block_hash.t ;
   fitness: MBytes.t list ;
   timestamp: Time.t ;
diff --git a/src/client/embedded/alpha/client_baking_forge.ml b/src/client/embedded/alpha/client_baking_forge.ml
index 09ac2d6ca..755be113f 100644
--- a/src/client/embedded/alpha/client_baking_forge.ml
+++ b/src/client/embedded/alpha/client_baking_forge.ml
@@ -61,13 +61,14 @@ let assert_valid_operations_hash shell_header operations =
         inconsistent header.")
 
 let inject_block cctxt
-    ?force ~shell_header ~priority ~seed_nonce_hash ~src_sk operations =
+    ?force ?net_id
+    ~shell_header ~priority ~seed_nonce_hash ~src_sk operations =
   assert_valid_operations_hash shell_header operations >>=? fun () ->
   let block = `Hash shell_header.Tezos_data.Block_header.predecessor in
   forge_block_header cctxt block
     src_sk shell_header priority seed_nonce_hash >>=? fun signed_header ->
   Client_node_rpcs.inject_block cctxt
-    ?force signed_header operations >>=? fun block_hash ->
+    ?force ?net_id signed_header operations >>=? fun block_hash ->
   return block_hash
 
 type error +=
@@ -174,8 +175,9 @@ let forge_block cctxt block
     let operations =
       if not best_effort then operations
       else List.map snd result.applied in
+    Client_node_rpcs.Blocks.info cctxt block >>=? fun {net_id} ->
     inject_block cctxt
-      ?force ~shell_header ~priority ~seed_nonce_hash ~src_sk
+      ?force ~net_id ~shell_header ~priority ~seed_nonce_hash ~src_sk
       [operations]
   else
     Lwt.return_error @@
@@ -507,7 +509,8 @@ let mine cctxt state =
         Fitness.pp shell_header.fitness >>= fun () ->
       Client_keys.get_key cctxt delegate >>=? fun (_,_,src_sk) ->
       inject_block cctxt.rpc_config
-        ~force:true ~shell_header ~priority ~seed_nonce_hash ~src_sk
+        ~force:true ~net_id:bi.net_id
+        ~shell_header ~priority ~seed_nonce_hash ~src_sk
         [List.map snd operations.applied]
       |> trace_exn (Failure "Error while injecting block") >>=? fun block_hash ->
       State.record_block cctxt level block_hash seed_nonce
diff --git a/src/client/embedded/alpha/client_baking_forge.mli b/src/client/embedded/alpha/client_baking_forge.mli
index cc615e0b6..101c06682 100644
--- a/src/client/embedded/alpha/client_baking_forge.mli
+++ b/src/client/embedded/alpha/client_baking_forge.mli
@@ -16,6 +16,7 @@ val generate_seed_nonce: unit -> Nonce.t
 val inject_block:
   Client_rpcs.config ->
   ?force:bool ->
+  ?net_id:Net_id.t ->
   shell_header:Block_header.shell_header ->
   priority:int ->
   seed_nonce_hash:Nonce_hash.t ->
diff --git a/src/client/embedded/demo/client_proto_main.ml b/src/client/embedded/demo/client_proto_main.ml
index 0265cff3c..5c8f75cd0 100644
--- a/src/client/embedded/demo/client_proto_main.ml
+++ b/src/client/embedded/demo/client_proto_main.ml
@@ -47,8 +47,7 @@ let mine cctxt =
           (cctxt.message "Cannot parse fitness: %a" Environment.Fitness.pp bi.fitness);
         exit 2 in
   Client_node_rpcs.forge_block_header cctxt.rpc_config
-    { shell = { net_id = bi.net_id ;
-                predecessor = bi.hash ;
+    { shell = { predecessor = bi.hash ;
                 proto_level = bi.proto_level ;
                 level = Int32.succ bi.level ;
                 timestamp = Time.now () ;
@@ -56,7 +55,7 @@ let mine cctxt =
                 validation_passes = 0 ;
                 operations_hash = Operation_list_list_hash.empty } ;
       proto = MBytes.create 0 } >>=? fun bytes ->
-  Client_node_rpcs.inject_block cctxt.rpc_config bytes [] >>=? fun hash ->
+  Client_node_rpcs.inject_block cctxt.rpc_config ~net_id:bi.net_id bytes [] >>=? fun hash ->
   cctxt.answer "Injected %a" Block_hash.pp_short hash >>= fun () ->
   return ()
 
diff --git a/src/environment/v1/tezos_data.mli b/src/environment/v1/tezos_data.mli
index fc51a3a94..9c7655846 100644
--- a/src/environment/v1/tezos_data.mli
+++ b/src/environment/v1/tezos_data.mli
@@ -74,7 +74,6 @@ end
 module Block_header : sig
 
   type shell_header = {
-    net_id: Net_id.t ;
     level: Int32.t ;
     (** The number of preceding block in this chain, i.e. the genesis
         has level 0. *)
diff --git a/src/jbuild b/src/jbuild
index e94b4e36f..385c793c3 100644
--- a/src/jbuild
+++ b/src/jbuild
@@ -24,7 +24,9 @@
 (executable
  ((name client_main)
   (public_name tezos-client)
-  (libraries (lwt utils client_lib client_embedded_genesis client_embedded_alpha))
+  (libraries (lwt utils client_lib
+              client_embedded_genesis
+              client_embedded_alpha))
   (flags (:standard -w -9+27-30-32-40@8
                     -safe-string
                     -linkall))
diff --git a/src/node/shell/distributed_db.ml b/src/node/shell/distributed_db.ml
index 8382d45a7..52dc75cfe 100644
--- a/src/node/shell/distributed_db.ml
+++ b/src/node/shell/distributed_db.ml
@@ -340,15 +340,27 @@ let state { disk } = disk
 let net_state { net_state } = net_state
 let db { global_db } = global_db
 
+let find_pending_block_header active_nets h =
+  Net_id.Table.fold
+    (fun _net_id net_db acc ->
+       match acc with
+       | Some _ -> acc
+       | None when Raw_block_header.Table.pending
+             net_db.block_header_db.table h ->
+           Some net_db
+       | None -> None)
+    active_nets
+    None
+
 let find_pending_operation active_nets h =
   Net_id.Table.fold
     (fun _net_id net_db acc ->
        match acc with
        | Some _ -> acc
-       | None ->
-           if Raw_operation.Table.pending net_db.operation_db.table h then
-             Some net_db
-           else None)
+       | None when Raw_operation.Table.pending
+             net_db.operation_db.table h ->
+           Some net_db
+       | None -> None)
     active_nets
     None
 
@@ -465,12 +477,17 @@ module P2p_reader = struct
                  P2p.try_send global_db.p2p state.conn (Block_header header))
           hashes
 
-    | Block_header block ->
-        may_handle state block.shell.net_id @@ fun net_db ->
+    | Block_header block -> begin
         let hash = Block_header.hash block in
-        Raw_block_header.Table.notify
-          net_db.block_header_db.table state.gid hash block >>= fun () ->
-        Lwt.return_unit
+        match find_pending_block_header state.peer_active_nets hash with
+        | None ->
+            (* TODO some penalty. *)
+            Lwt.return_unit
+        | Some net_db ->
+            Raw_block_header.Table.notify
+              net_db.block_header_db.table state.gid hash block >>= fun () ->
+            Lwt.return_unit
+      end
 
     | Get_operations (net_id, hashes) ->
         may_handle state net_id @@ fun net_db ->
@@ -720,7 +737,6 @@ let clear_block net_db hash n =
 
 let commit_block net_db hash header operations result =
   assert (Block_hash.equal hash (Block_header.hash header)) ;
-  assert (Net_id.equal (State.Net.id net_db.net_state) header.shell.net_id) ;
   assert (List.length operations = header.shell.validation_passes) ;
   State.Block.store net_db.net_state header operations result >>=? fun res ->
   clear_block net_db hash header.shell.validation_passes ;
@@ -728,21 +744,10 @@ let commit_block net_db hash header operations result =
 
 let commit_invalid_block net_db hash header _err =
   assert (Block_hash.equal hash (Block_header.hash header)) ;
-  assert (Net_id.equal (State.Net.id net_db.net_state) header.shell.net_id) ;
   State.Block.store_invalid net_db.net_state header >>=? fun res ->
   clear_block net_db hash header.shell.validation_passes ;
   return res
 
-let inject_block_header net_db h b =
-  fail_unless
-    (Net_id.equal
-       b.Block_header.shell.net_id
-       (State.Net.id net_db.net_state))
-    (failure "Inconsitent net_id in operation") >>=? fun () ->
-  Raw_block_header.Table.inject
-    net_db.block_header_db.table h b >>= fun res ->
-  return res
-
 let inject_operation net_db h op =
   assert (Operation_hash.equal h (Operation.hash op)) ;
   Raw_operation.Table.inject net_db.operation_db.table h op >>= fun res ->
diff --git a/src/node/shell/node.ml b/src/node/shell/node.ml
index e2181be5e..7daa2d220 100644
--- a/src/node/shell/node.ml
+++ b/src/node/shell/node.ml
@@ -40,9 +40,9 @@ let inject_protocol state ?force:_ proto =
   in
   Lwt.return (hash, validation)
 
-let inject_block validator ?force bytes operations =
+let inject_block validator ?force ?net_id bytes operations =
   Validator.validate_block
-    validator ?force bytes operations >>=? fun (hash, block) ->
+    validator ?force ?net_id bytes operations >>=? fun (hash, block) ->
   return (hash, (block >>=? fun _ -> return ()))
 
 type t = {
@@ -52,6 +52,7 @@ type t = {
   mainnet_validator: Net_validator.t ;
   inject_block:
     ?force:bool ->
+    ?net_id:Net_id.t ->
     MBytes.t -> Operation.t list list ->
     (Block_hash.t * unit tzresult Lwt.t) tzresult Lwt.t ;
   inject_operation:
@@ -165,7 +166,7 @@ module RPC = struct
     Context.get_test_network context >>= fun test_network ->
     Lwt.return {
       hash ;
-      net_id = header.shell.net_id ;
+      net_id = State.Block.net_id block ;
       level = header.shell.level ;
       proto_level = header.shell.proto_level ;
       predecessor = header.shell.predecessor ;
@@ -203,17 +204,13 @@ module RPC = struct
 
   let get_validator_per_hash node hash =
     State.read_block_exn node.state hash >>= fun block ->
-    let header = State.Block.header block in
-    if Net_id.equal
-        (Net_validator.net_id node.mainnet_validator)
-        header.shell.net_id then
+    let net_id = State.Block.net_id block in
+    if Net_id.equal (Net_validator.net_id node.mainnet_validator) net_id then
       Lwt.return (Some node.mainnet_validator)
     else
       match Net_validator.child node.mainnet_validator with
       | Some test_validator ->
-          if Net_id.equal
-              (Net_validator.net_id test_validator)
-              header.shell.net_id then
+          if Net_id.equal (Net_validator.net_id test_validator) net_id then
             Lwt.return_some test_validator
           else
             Lwt.return_none
@@ -253,6 +250,7 @@ module RPC = struct
         Chain.head net_state >>= fun head ->
         let head_header = State.Block.header head in
         let head_hash = State.Block.hash head in
+        let head_net_id = State.Block.net_id head in
         State.Block.context head >>= fun head_context ->
         Context.get_protocol head_context >>= fun head_protocol ->
         Prevalidator.context pv >>= function
@@ -284,7 +282,7 @@ module RPC = struct
                        operations) ;
                 operations = Some operations ;
                 data = MBytes.of_string "" ;
-                net_id = head_header.shell.net_id ;
+                net_id = head_net_id ;
                 test_network ;
               }
 
@@ -351,7 +349,6 @@ module RPC = struct
                 Updater.block_hash = prevalidation_hash ;
                 block_header = {
                   shell = {
-                    net_id = head_header.shell.net_id ;
                     level = Int32.succ head_header.shell.level ;
                     proto_level ;
                     predecessor = head_hash ;
@@ -495,7 +492,6 @@ module RPC = struct
       else
         ((pred_shell_header.proto_level + 1) mod 256) in
     let shell_header : Block_header.shell_header = {
-      net_id = pred_shell_header.net_id ;
       level = Int32.succ pred_shell_header.level ;
       proto_level ;
       predecessor = State.Block.hash predecessor ;
diff --git a/src/node/shell/node.mli b/src/node/shell/node.mli
index 56cf8f744..0c058a850 100644
--- a/src/node/shell/node.mli
+++ b/src/node/shell/node.mli
@@ -35,7 +35,7 @@ module RPC : sig
   type block_info = Node_rpc_services.Blocks.block_info
 
   val inject_block:
-    t -> ?force:bool ->
+    t -> ?force:bool -> ?net_id:Net_id.t ->
     MBytes.t -> Operation.t list list ->
     (Block_hash.t * unit tzresult Lwt.t) tzresult Lwt.t
   (** [inject_block node ?force bytes] tries to insert [bytes]
diff --git a/src/node/shell/node_rpc_services.ml b/src/node/shell/node_rpc_services.ml
index b3605eb77..6c607cb80 100644
--- a/src/node/shell/node_rpc_services.ml
+++ b/src/node/shell/node_rpc_services.ml
@@ -81,14 +81,14 @@ module Blocks = struct
              fitness ; timestamp ; protocol ;
              validation_passes ; operations_hash ; data ;
              operations ; test_network } ->
-        ((hash, operations, protocol, test_network),
+        ((hash, net_id, operations, protocol, test_network),
          { Block_header.shell =
-             { net_id ; level ; proto_level ; predecessor ;
+             { level ; proto_level ; predecessor ;
                timestamp ; validation_passes ; operations_hash ; fitness } ;
            proto = data }))
-      (fun ((hash, operations, protocol, test_network),
+      (fun ((hash, net_id, operations, protocol, test_network),
             { Block_header.shell =
-                { net_id ; level ; proto_level ; predecessor ;
+                { level ; proto_level ; predecessor ;
                   timestamp ; validation_passes ; operations_hash ; fitness } ;
               proto = data }) ->
         { hash ; net_id ; level ; proto_level ; predecessor ;
@@ -97,8 +97,9 @@ module Blocks = struct
           operations ; test_network })
       (dynamic_size
          (merge_objs
-            (obj4
+            (obj5
                (req "hash" Block_hash.encoding)
+               (req "net_id" Net_id.encoding)
                (opt "operations" (dynamic_size (list (dynamic_size (list (dynamic_size operation_encoding))))))
                (req "protocol" Protocol_hash.encoding)
                (dft "test_network"
@@ -602,16 +603,17 @@ type inject_block_param = {
   raw: MBytes.t ;
   blocking: bool ;
   force: bool ;
+  net_id: Net_id.t option ;
   operations: Operation.t list list ;
 }
 
 let inject_block_param =
   conv
-    (fun { raw ; blocking ; force ; operations } ->
-       (raw, blocking, force, operations))
-    (fun (raw, blocking, force, operations) ->
-       { raw ; blocking ; force ; operations })
-    (obj4
+    (fun { raw ; blocking ; force ; net_id ; operations } ->
+       (raw, blocking, force, net_id, operations))
+    (fun (raw, blocking, force, net_id, operations) ->
+       { raw ; blocking ; force ; net_id ; operations })
+    (obj5
        (req "data" bytes)
        (dft "blocking"
           (describe
@@ -627,6 +629,7 @@ let inject_block_param =
                 the current head. (default: false)"
              bool)
           false)
+       (opt "net_id" Net_id.encoding)
        (req "operations"
           (describe
              ~description:"..."
diff --git a/src/node/shell/node_rpc_services.mli b/src/node/shell/node_rpc_services.mli
index 68534031c..6977efb10 100644
--- a/src/node/shell/node_rpc_services.mli
+++ b/src/node/shell/node_rpc_services.mli
@@ -177,6 +177,7 @@ type inject_block_param = {
   raw: MBytes.t ;
   blocking: bool ;
   force: bool ;
+  net_id: Net_id.t option ;
   operations: Operation.t list list ;
 }
 
diff --git a/src/node/shell/state.ml b/src/node/shell/state.ml
index 382321d3b..1755cf441 100644
--- a/src/node/shell/state.ml
+++ b/src/node/shell/state.ml
@@ -142,9 +142,7 @@ type t = global_state
 module Locked_block = struct
 
   let store_genesis store genesis commit =
-    let net_id = Net_id.of_block_hash genesis.block in
     let shell : Block_header.shell_header = {
-      net_id ;
       level = 0l ;
       proto_level = 0 ;
       predecessor = genesis.block ;
@@ -350,8 +348,8 @@ module Block = struct
   let hash { hash } = hash
   let header { contents = { header } } = header
   let net_state { net_state } = net_state
+  let net_id { net_state = { net_id } } = net_id
   let shell_header { contents = { header = { shell } } } = shell
-  let net_id b = (shell_header b).net_id
   let timestamp b = (shell_header b).timestamp
   let fitness b = (shell_header b).fitness
   let level b = (shell_header b).level
diff --git a/src/node/shell/validator.ml b/src/node/shell/validator.ml
index 3b5871e9f..95e2bd8e1 100644
--- a/src/node/shell/validator.ml
+++ b/src/node/shell/validator.ml
@@ -56,14 +56,37 @@ let get v net_id =
   try get_exn v net_id >>= fun nv -> return nv
   with Not_found -> fail (Inactive_network net_id)
 
-let validate_block v ?force bytes operations =
+let validate_block v ?(force = false) ?net_id bytes operations =
   let hash = Block_hash.hash_bytes [bytes] in
   match Block_header.of_bytes bytes with
   | None -> failwith "Cannot parse block header."
   | Some block ->
-      get v block.shell.net_id >>=? fun nv ->
+      begin
+        match net_id with
+        | None -> begin
+            Distributed_db.read_block_header
+              v.db block.shell.predecessor >>= function
+            | None ->
+                failwith "Unknown predecessor (%a), cannot inject the block."
+                  Block_hash.pp_short block.shell.predecessor
+            | Some (net_id, _bh) -> get v net_id
+          end
+        | Some net_id ->
+            get v net_id >>=? fun nv ->
+            if force then
+              return nv
+            else
+              Distributed_db.Block_header.known
+                (Net_validator.net_db nv)
+                block.shell.predecessor >>= function
+              | true ->
+                  return nv
+              | false ->
+                  failwith "Unknown predecessor (%a), cannot inject the block."
+                    Block_hash.pp_short block.shell.predecessor
+      end >>=? fun nv ->
       let validation =
-        Net_validator.validate_block nv ?force hash block operations in
+        Net_validator.validate_block nv ~force hash block operations in
       return (hash, validation)
 
 let shutdown { active_nets ; block_validator } =
diff --git a/src/node/shell/validator.mli b/src/node/shell/validator.mli
index c22484830..48fb954b0 100644
--- a/src/node/shell/validator.mli
+++ b/src/node/shell/validator.mli
@@ -30,6 +30,7 @@ val get_exn: t -> Net_id.t -> Net_validator.t Lwt.t
 val validate_block:
   t ->
   ?force:bool ->
+  ?net_id:Net_id.t ->
   MBytes.t -> Operation.t list list ->
   (Block_hash.t * State.Block.t tzresult Lwt.t) tzresult Lwt.t
 
diff --git a/src/proto/alpha/block_header_repr.ml b/src/proto/alpha/block_header_repr.ml
index 1d3e16a16..14734cbe8 100644
--- a/src/proto/alpha/block_header_repr.ml
+++ b/src/proto/alpha/block_header_repr.ml
@@ -81,14 +81,14 @@ type error +=
   | Cant_parse_proto_header
 
 let parse
-    ({ shell = { net_id ; level ; proto_level ; predecessor ;
+    ({ shell = { level ; proto_level ; predecessor ;
                  timestamp ; fitness ; validation_passes ; operations_hash } ;
        proto } : Block_header.t) : block_header tzresult =
   match Data_encoding.Binary.of_bytes signed_proto_header_encoding proto with
   | None -> Error [Cant_parse_proto_header]
   | Some (proto, signature) ->
       let shell =
-        { Block_header.net_id ; level ; proto_level ; predecessor ;
+        { Block_header.level ; proto_level ; predecessor ;
           timestamp ; fitness ; validation_passes ; operations_hash } in
       Ok { shell ; proto ; signature }
 
diff --git a/src/proto/genesis/services.ml b/src/proto/genesis/services.ml
index b267724ea..ab07f8655 100644
--- a/src/proto/genesis/services.ml
+++ b/src/proto/genesis/services.ml
@@ -64,9 +64,9 @@ let rpc_services : Updater.rpc_context RPC.directory =
     RPC.register
       dir
       (Forge.block RPC.Path.root)
-      (fun _ctxt ((net_id, level, proto_level, predecessor,
+      (fun _ctxt ((_net_id, level, proto_level, predecessor,
                    timestamp, fitness), command) ->
-        let shell = { Block_header.net_id ; level ; proto_level ; predecessor ;
+        let shell = { Block_header.level ; proto_level ; predecessor ;
                       timestamp ; fitness ; validation_passes = 1 ; operations_hash } in
         let bytes = Data.Command.forge shell command in
         RPC.Answer.return bytes) in
diff --git a/src/utils/tezos_data.ml b/src/utils/tezos_data.ml
index 0de45afe8..f82238b9e 100644
--- a/src/utils/tezos_data.ml
+++ b/src/utils/tezos_data.ml
@@ -164,7 +164,6 @@ end
 module Block_header = struct
 
   type shell_header = {
-    net_id: Net_id.t ;
     level: Int32.t ;
     proto_level: int ; (* uint8 *)
     predecessor: Block_hash.t ;
@@ -177,16 +176,15 @@ module Block_header = struct
   let shell_header_encoding =
     let open Data_encoding in
     conv
-      (fun { net_id ; level ; proto_level ; predecessor ;
+      (fun { level ; proto_level ; predecessor ;
              timestamp ; validation_passes ; operations_hash ; fitness } ->
-        (net_id, level, proto_level, predecessor,
+        (level, proto_level, predecessor,
          timestamp, validation_passes, operations_hash, fitness))
-      (fun (net_id, level, proto_level, predecessor,
+      (fun (level, proto_level, predecessor,
             timestamp, validation_passes, operations_hash, fitness) ->
-        { net_id ; level ; proto_level ; predecessor ;
+        { level ; proto_level ; predecessor ;
           timestamp ; validation_passes ; operations_hash ; fitness })
-      (obj8
-         (req "net_id" Net_id.encoding)
+      (obj7
          (req "level" int32)
          (req "proto" uint8)
          (req "predecessor" Block_hash.encoding)
diff --git a/src/utils/tezos_data.mli b/src/utils/tezos_data.mli
index bf987f9b7..7eed25720 100644
--- a/src/utils/tezos_data.mli
+++ b/src/utils/tezos_data.mli
@@ -66,7 +66,6 @@ end
 module Block_header : sig
 
   type shell_header = {
-    net_id: Net_id.t ;
     level: Int32.t ;
     proto_level: int ; (* uint8 *)
     predecessor: Block_hash.t ;
diff --git a/test/shell/test_state.ml b/test/shell/test_state.ml
index dcb6f6d77..55524eeb0 100644
--- a/test/shell/test_state.ml
+++ b/test/shell/test_state.ml
@@ -68,7 +68,6 @@ let block _state ?(operations = []) pred_hash pred name : Block_header.t =
   let fitness = incr_fitness pred.Block_header.shell.fitness in
   let timestamp = incr_timestamp pred.shell.timestamp in
   { shell = {
-        net_id = pred.shell.net_id ;
         level = Int32.succ pred.shell.level ;
         proto_level = pred.shell.proto_level ;
         predecessor = pred_hash ;
@@ -111,8 +110,7 @@ let block _state ?(operations = []) (pred: State.Block.t) name
   let pred_header = State.Block.shell_header pred in
   let fitness = incr_fitness pred_header.fitness in
   let timestamp = incr_timestamp pred_header.timestamp in
-  { shell = { net_id = pred_header.net_id ;
-              level = Int32.succ pred_header.level ;
+  { shell = { level = Int32.succ pred_header.level ;
               proto_level = pred_header.proto_level ;
               predecessor = State.Block.hash pred ;
               validation_passes = 1 ;
diff --git a/test/shell/test_store.ml b/test/shell/test_store.ml
index 802d91523..2380369ac 100644
--- a/test/shell/test_store.ml
+++ b/test/shell/test_store.ml
@@ -82,7 +82,6 @@ let lolblock ?(operations = []) header =
           { timestamp = Time.of_seconds (Random.int64 1500L) ;
             level = 0l ; (* dummy *)
             proto_level = 0 ; (* dummy *)
-            net_id ;
             validation_passes = Random.int 32 ;
             predecessor = genesis_block ; operations_hash ;
             fitness = [MBytes.of_string @@ string_of_int @@ String.length header;